.\" -*- nroff -*-
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright 2014 Los Alamos National Security, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Get 3 "Jun 10, 2020" "4.0.4" "Open MPI"
.SH NAME
\fBMPI_Get\fP, \fBMPI_Rget\fP \- Copies data from the target memory to the origin.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
MPI_Get(void *\fIorigin_addr\fP, int \fIorigin_count\fP, MPI_Datatype
	\fIorigin_datatype\fP, int \fItarget_rank\fP, MPI_Aint \fItarget_disp\fP,
	int \fItarget_count\fP, MPI_Datatype \fItarget_datatype\fP, MPI_Win \fIwin\fP)

MPI_Rget(void *\fIorigin_addr\fP, int \fIorigin_count\fP, MPI_Datatype
	 \fIorigin_datatype\fP, int \fItarget_rank\fP, MPI_Aint \fItarget_disp\fP,
	 int \fItarget_count\fP, MPI_Datatype \fItarget_datatype\fP, MPI_Win \fIwin\fP,
         MPI_Request *\fIrequest\fP)

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
origin_addr
Initial address of origin buffer (choice).
.TP 1i
origin_count
Number of entries in origin buffer (nonnegative integer).
.TP 1i
origin_datatype
Data type of each entry in origin buffer (handle).
.TP 1i
target_rank
Rank of target (nonnegative integer).
.TP 1i
target_disp
Displacement from window start to the beginning of the target buffer (nonnegative integer).
.TP 1i
target_count
Number of entries in target buffer (nonnegative integer).
.TP 1i
target datatype
datatype of each entry in target buffer (handle)
.TP 1i
win
window object used for communication (handle)

.SH OUTPUT PARAMETER
.ft R
.TP li
request
MPI_Rget: RMA request
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
\fBMPI_Get\fP copies data from the target memory to the origin, similar to MPI_Put, except that the direction of data transfer is reversed. The \fIorigin_datatype\fP may not specify overlapping entries in the origin buffer. The target buffer must be contained within the target window, and the copied data must fit, without truncation, in the origin buffer. Only processes within the same node can access the target window.
.sp

\fBMPI_Rget\fP is similar to \fBMPI_Get\fP, except that it allocates a communication request object and associates it with the request handle (the argument \fIrequest\fP) that can be used to wait or test for completion. The completion of an MPI_Rget operation indicates that the data is available in the origin buffer. If \fIorigin_addr\fP points to memory attached to a window, then the data becomes available in the private copy of this window.

.SH FORTRAN 77 NOTES
.ft R
The MPI standard prescribes portable Fortran syntax for
the \fITARGET_DISP\fP argument only for Fortran 90. FORTRAN 77
users may use the non-portable syntax
.sp
.nf
     INTEGER*MPI_ADDRESS_KIND \fITARGET_DISP\fP
.fi
.sp
where MPI_ADDRESS_KIND is a constant defined in mpif.h
and gives the length of the declared integer in bytes.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

.SH SEE ALSO
.ft R
.sp
MPI_Put

